1. Field of the Invention
The invention relates in general to an electronic apparatus, and more particularly to an electronic apparatus having an antenna disposed on a surface of a housing of the apparatus.
2. Description of the Related Art
FIG. 1 is a schematic illustration showing a structure of a conventional electronic apparatus 10. Referring to FIG. 1, the electronic apparatus 10, such as a mobile telephone, includes a housing 110, a circuit board 120 and an antenna device 130. The circuit board 120 of the conventional electronic apparatus 10 is placed inside the housing 110. The antenna device 130 is mounted to the circuit board 120 to transmit and receive a wireless signal. The antenna device 130 includes, for example, a chip antenna or planar inverted F antenna (PIFA).
The efficiency of the conventional electronic apparatus 10 of receiving and transmitting the wireless signal depends on the antenna gain and the return loss of the antenna device 130. The antenna gain is the ratio of the wireless signal before being transmitted to the wireless signal after being received, and the return loss is the ratio of the wireless signal after return to the wireless signal before return.
However, because the antenna device 130 of the conventional electronic apparatus 10 is mounted to the circuit board 120, the antenna device 130 tends to be interfered with other electronic elements, such as capacitors or transformers, in the circuit board 120, and the antenna gain and the return loss of the antenna device 130 tend to be influenced seriously. In general, the antenna gain of the conventional electronic apparatus 10 is usually a negative value, and the specified value of the return loss is usually less than −7 dB.
In addition, if the antenna device 130 is mounted to the circuit board 120, the available layout space in the circuit board 120 is correspondingly decreased and the layout difficulty of the circuit board 120 is also increased.